Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.47	5.144%	$104.5867	$104.59	$104.60	$104.60
Purchase #2	$94.43	5.452%	$99.5783	$99.58	$99.60	$99.60
Purchase #3	$154.74	11.114%	$171.9378	$171.94	$171.95	$171.90
Purchase #4	$121.87	9.310%	$133.2161	$133.22	$133.20	$133.20
Purchase #5	$62.42	5.270%	$65.7095	$65.71	$65.70	$65.70
Purchase #6	$167.63	6.793%	$179.0171	$179.02	$179.00	$179.00
Purchase #7	$94.67	6.280%	$100.6153	$100.62	$100.60	$100.60
7 purchase totals =	$795.23		$854.6608	$854.68	$854.65	$854.60